In fact, mods actually can be turned on and switched between; brightness change while switching between the original game and my mod shows it prefectly (I set brightness in the original to 40% and 60% in mod). The actual question is how to make a .gro to be loaded from the mod's folder?

While I do work for Croteam, I'm first of all of this community, so my opinions are my own and do not represent Croteam's views.Unless when I use this nice blue color I totally didn't steal from Blizzard.

Oh wait... that's what you meant.. I have gotten it to list Serious Sam Forever and it loaded it, but because it isn't actually compatible with the steam version it crashes as soon as you try to load a map.

Do you have an .nfo and .mod file with the same name as your mod folder name?